Pitch indicator for musical instruments



Jan. 7, 1930. T, N, MIR E D 1,742,869

PITCH INDICATOR FOR MUSICAL- INSTRUMENTS Filed April 20. 1928 2 Sheets-Sheei 1 Jan. 7, 1930.

T. N. MIRFIELD 1,742,869

PITCH INDICATOR FOR MUSICAL INSTRUMENTS Filed April 20. 1928 2 Sheets-Sheet 2 Patented Jan. 7, 1930 UNITED STATES PATENT OFFICE THEON NUMA MIRFIELD, OF TOORAK, AUSTRALIA, ASSIGNOR OF ONE-HALF TO HENRY JOHN WEST, OF SYDNEY, AUSTRALIA PITCH INDICATOR FOR MUSICAL INSTRUMENTS Application filed April 20, 1928, Serial No. 271,425, and. in Australia May 25, 1927.

This invention relates to a pitch indicator for musical instruments and refers especially but is not limited to a device for indicating the note emitted by a musical instrument of relatively low pitch, such as a drum, tympanum, double bass or like instrument, whereby the same may be tuned to the required note.

It is frequently necessary to tune a drum or tympanum during the playing of a musi- 2 of adjustment has been, up to the present, de-

pendent upon the ear of the instrumentalist.

Now, the object of the present invention is to provide a device of simple and compact construction adapted to give a visual indication of the note being emitted by a musical instrument.

I accomplish the abovementioned object by providing an indicator having one or more tuned reeds, and means for imparting,

to the tuned reed 0r reeds, forced vibrations corresponding to those executed by av vibratory portion of a musical instrument, whereby, when resonance occurs between one of the reeds and a component of the said vibration, its greater amplitude will indicate the note being emitted by the instrument.

In this invention, I avail myself of the well known natural phenomenon-known as resonancethat, when forced vibrations are imparted to a vibratory member, the amplitude of the resultant movement is not pronounced unless the natural frequency of the said member is identical with that of the forced vibrations imparted thereto. Consequently, by providing means whereby the v1- .brations of a musical instrument are transmitted to one or more tuned reeds, an indication of the pitch of the note emanating from 50 the said instrument can be obtained from the resonance of the particular reed in sympathy therewith.

More particularly the invention comprises a plurality of tuned reeds fitted to a rocking member, an arm on the rocking member adapted to bear against a vibratory portion of a musical instrument and thereby impart forced vibrations to the tuned reeds, and means for observing the amplitude of the reeds when the instrument is being sounded.

The movement of the tuned reeds may, if desired, be magnified by means of a beam of light projected on to reflectors on the reeds and directed therefrom to a conveniently arranged indicating surface provided with a scale.

Having briefly described the object and nature of the invention, reference will now be had to the accompanying sheets of explanatory drawings wherein Figure 1 is a view in sectional elevation of a tympanum fitted with a pitch indicator constructed and arranged in accordance with the present invention.

Figure 2 is a view in sectional side elevation of the indicator shown in Figure 1 and is drawn to a larger scale.

Figure 3 is a view in front elevation of the indicator shown in Figure 2.

Figure 4 is a view similar to Figure 2 and shows the position assumed by the various parts when the indicator is not in use.

Figure 5 is a view in perspective of a detail of the invention and hereinafter is fully described.

Figure 6 is a view in plan of Figure 1, parts being broken away for convenience of illustration, this view being drawn to a smaller scale than Figure 1 Figure 7 is a View in sectional elevation of reflectors and mountings therefor.

Figure 8 is a view in plan of Figure 7 parts being broken away for convenience of illustration.

Figure 9 is a view in sectional side elevation of a modified form of the invention fitted to a membranous instrument.

Figure 10 is a View of portion of the indicator shown in Figure 9, taken in the direction of the arrow shown therein.

Figure 11 is a fragmentary view showing a modified form of the invention illustrated in Figure 9.

Whilst, in the drawings, the invention is illustrated asapplied to a membranous instrument, it will be obvious that it may be applied with equal facility to other instrunu-znts e. g., to a double bass, cello or the like.

Refering to Figure 1 of the drawings, the reference numeral 12 designates the body of a tympanum having a membrane 13 fitted to the top thereof and adapted to be retained in position by means of a flanged ring 14 engaging a hoop 15 at the periphery of the membrane. In order to tune the instrument, the membrane 13 is adapted to be placed under tension by means of hand tension screws 16 fitted to the flanged ring 14 and engaging brackets 17 on the body of the instrument, or, if preferred, any other foot or hand operated device of known construction may be employed for effecting this adjustment.

A bracket 18 is fitted to the inner periphery of the body adjacent to the membrane and is secured in position by approved means not indicated in the drawings. This bracket is provi ded with integrally formed extensions 19 to which are fitted, by means of screws 20, re-

.silient metallic strips 21 having their free ends rigidly secured to opposite ends of a transverse rocking bar 22. The rocking bar is provided with a plurality of holes adapted to accommodate pins 23 fitted rigidly to upwardly and forwardly projecting metallic 5 reeds 24.

The reeds may be loaded at their free ends by strips 25 whereby the same may be ad preferably vary progressively from one end of the rocking bar to the other and are adapted to cover the whole range of notes within the compass of the instrument.

Means are provided whereby the membrane, or other oscillating member of the musical instrument, transmits forced vibrations to the said reeds 24 either mechanically or otherwise. In the accompanying drawings, I have illustrated mechanical means for transmitting these forced vibrations to the said reeds 24, but it will be understood that electrical or other means may be employed as hereinafter described.

An arm 26 is fitted rigidly at one end to the rocking bar 22 andprojects forwardly and upwardly as indicated in Figures 1 and 2 of the drawings. The free end of this arm is fitted with a pad 27 of felt which is adapted to bear against the underside of the membrane 13 so that, when the latter is vibrating, its movement is mechanically transmitted to the rocking bar 22.

Partitions 28 may, if preferred, be fitted to the rocking arm between adjacent reeds and the same may be connected beyond the extremities of the reeds by means of a transverse 29 whereby the partitions are maintained in correct relative relationship and form cells or open compartments for the said reeds 24.

A projection device 30 may be fitted to the bowl 12 of the instrument and arranged to direct a beam of light as 31 from a lamp 32 on to a series of mirrors 33 fitted to the undersides of the free ends ofthe reeds 24. The beam 31 is reflected by the mirrors 33 on to a series of reflectors -34 arranged within and near the bottom of the body of the instrument and these mirrors reflect the beams upwardly onto the membrane 13 and approximately along a diameter thereof as shown at 31 in plan in Figure 6 of the drawings.

These areas or patches of light 3.1 are visible from above the instrument owing to the translucent nature of the membrane and if preferred a scale 35 may be painted or otherwise provided on the same opposite to the illustrated portions thereof. The reflectors 34 of which there is one to each reed 24 may be adjustably mounted in brackets 36 of angle cross section fitted to the inner surface of the body of the tympanum. The mirrors 34 are mounted in holders 37, which are secured by means of screws 38 to the underside of the angle shaped brackets 36 and.

springs 39 are located between the underside of the brackets and the adjacent faces of the holders.

In the construction shown in the drawings (see Figures7'and 8) two screws 38 are pro- VlClQCl at one end of the holder and onescrew at the opposite end thereof, whereby each mirror or reflector 34 may be tilted in two planes at right angles to each other in order that the position-of the respective illumi-.

nated area 31 on the membrane 13 may be adjusted in position'until it is disposed in correct relation to the scale 35.

It will be obvious, however, that these re flectors may be adjustably supported in any other suitable manner.

A pair of horizontal spindles 40 and 41 are rotativelymounted in the bracket 18, and

the lower spindle 40 is provided with upwardly and forwardly extending arms 42..

disposed adjacent to the opposite ends of the rocking bar 22.

A transverse holder 43 rigidly connects the arms 42 and supports a strip of felt 44 adapted to function as a damper. v One of the levers 42 is provided with an upwardly extending arm 45 which is'connected by means of a tension spring 46 to a block 47 mounted in a guide 48 and adapted to be adjusted as required by means of a screw 49 fitted to the bracket 18.

A boss 50 is formed integrally with the bracket 18 and is disposed adjacent to one of the lower corners thereof and the same is adapted to rotatively support a circular cam 51 fitted to a horizontal control rod 52. A depending arm 53 is formed integrally with the arms 42 and and the lower end thereof is provided with an adjusting screw 54 adapted to bear against the face of the circular cam 51.

The spindle 41 is fitted with a pair of downwardly and forwardly extending arms 55, the free ends of which are connected by springs 56 to the free ends of the arms 42, and a transverse holder 57 rigidly connects the arms and is provided with a pad of felt 59 arrangedbelow the reeds 24.

The bosses of the arms 55 are provided with lugs 58 which are adapted to be engaged by the ends of adjustment screws 60 fitted to the arms 42 on the lower spindle 40.

hen the control rod 52 is partially rotated by means of a crank 61 on the projecting end thereof, so that the adjustment screw on the lower end of the arm 53 engages the lower portion of the circular cam 51, the spring 46 displaces the lever 42 and causes the pad of felt 44 to engage the upper faces of the reeds 24, at the same time depressing the arm 26 until the pad on the upper end thereof is removed from the underside of the membrane 13.

This partial movement of the spindle 40 and the arms fitted thereto removes the adjustable stops 60 from the lugs 58 and permits of the springs 56 raising the arms 55 until the felt pad 59 is engaging the underside of the tuned reeds 54 (see Figure 4 of the drawings) When, however, the control rod 52 is moved so that the high part of the circular cam is engaged by the screw on the lower end of the arm 53, the arms 42 and 55 are moved into the position indicated in Figure 2 of the drawings, and the arm 26 is released to permit of a partial movement of the rocking bar 22 until the pad 27 engages the membrane.

When the instrument is sounded, the vibrations of the membrane are communicated by the arm 26 to the rocking bar 22 and forced vibrations are imparted thereby to the tuned reeds 24.

It is well known that, when forced vibrations are imparted to vibratory members, the amplitude of the resultant movement is not pronounced unless the natural frequency of vibration of the said vibratory members is identical with that of the forced vibrations imparted thereto-this conditionbeingknown as resonance. Consequently, the movement of the lighted patches 31 on the membrane 13 of the instrument reflected from the reeds 24 is not appreciable except in the case of one corresponding to a reed which is in resonance with the vibrating membrane and hence with the note emitted by the instrument. This condition is illustrated in Figure 6 of the drawings where the note g. is represented as being surrounded by the instrument and the amplitude of the beam of light disposed in alignment therewith is considerably greater than, and is readily distinguished from, the movement of the'adj acent beams.

The vibrations executed by a stretched diaphragm, when struck, are of a complex character, for, as well as harmonics of the fundamental note being present, inharmonics or extraneous notes are usually produced simultaneously; consequently, the reeds 24 may be so tuned as to resonate either with the fundamental note or with one of the harmonic or inharmonic notes simultaneously emitted by the instrument. These remarks also apply to other musical instruments to which the indicator may be fitted.

If referred, a switch 52 may be fitted to the control rod 52 and'adapted to complete the circuit of the lamp 32 when the dampers 44 and 59 are removed from the reeds 24 upon the partial movement of the control rod.

In an alternative form of the invention (see Figure 9 of the drawings), the indicating device may be mounted on a support 62 and secured to the outer periphery of the body 12 of the instrument.

A bracket 18 is secured to the support 62 and the same carries a rocking bar 22 fitted with a plurality of turned reeds 24 as described with reference to the construction illustrated in Figures 1 to 4 of the drawings.

The free ends of the reeds pass through a slot 63 formed in a plate 64 and the said ends are enlarged as at 65 whereby the movements thereof may be observed through a sheet of.

glass 66 fitted to the top of the casing 67 If preferred, a lamp 68 may be mounted within the casing and arranged to illuminate the enlarged ends 65 of the tuned reeds whereby their movement may be made clearly observed. In this case, the vibratory movements of the reeds are observed directly through the glass 66 provided for that purpose.

In a modified form of the invention (see Figure 11), the arm 26 may be pivotally mounted on a bracket 69 rigidly secured to the rocking bar 22 and an extension on the bracket is connected by means of a spring 70 to the said arm.

A cam 71 is oscillatively mounted on the bracket 69 and the spring 70 maintains the upper edge of the arm 24 in engagement therewith. A lever 72 is arranged in fixed relationship with the cam and is adapted to be actuated by approved means, not shown in the drawings. In the position indicated in Figure 11, the cam 71 maintains the arm 26 in engagement with an adjustment screw 7 3 on the bracket 69 and with the membrane of the instrument, and when a partial movement is imparted to the cam in the direction indicated by the arrow in that figure, the arm 26 will be withdrawn from the membrane by means of the tension spring70.

When an indicating device constructed as hereinbefore described is to be fitted to an instrument such as a double bass, or a cello it may be so mounted thereon that the pad on the end of the arm 26 bears against the sound box adjacent to the bridge.

In lieu of mechanically transmitting the vibrations from the instrument to the indicator as hereinbefore described, forced vibrations may be imparted to the reeds by electrical or other means.

For example an electromagnet may be arranged adjacent to the rocking bar and adapted when alternately energized and de-energized to vibrate the tuned reeds, and means may be associated with a Vibrating portion of the musical instrument for effecting the periodic energization and de-energization of the said electro-magnet.

Alternatively, advantage may be taken of the passage of sound waves through the air for actuating a diaphragm mechanically or electrically associated with the rocking .ba-r carrying the tuned reeds whereby synchronous vibrations may be imparted thereto.

I claim 1. In a pitch indicator for a musical instrument, one or more tuned vibratory memhers, means for imparting to the said vibratory member or members forced vibrations corresponding to the note being emitted by the musical instrument, and means for observing the amplitudes of the said vibratory member or members.

2. In a pitch indicator for a musical instrument, a plurality of tuned reeds, means for imparting to the tuned reeds forced vibrations corresponding to the note emitted by the musical instrument whereby resonance will occur between one of the reeds and a component of the said note, and means for observing the amplitudes of the said reeds.

3. In a pitch indicator for a musical instrument according to claim 2, means for mechanically communicating vibrations from a vibratory portion of the instrument to the tuned reeds.

4. In a pitch indicator for a musical instrument according to claim 2, electro-1nagnetic means associated with a vibratory portion of the instrument and with the tuned reeds for effecting the transference of vibrations to the said tuned reeds.

5. In a pitch indicator for musical instruments according to claim '2, reflectors on the reeds, means for projecting a beam of light to the reflectors and an indicating surface disposed in the path of the reflected beam.

6. In a pitch indicator for a musical instrument, a plurality of tuned reeds fitted to a rocking member and an arm on the rock ing member adapted to bear against a vibratory portion of the musical instrument and impart forced vibrations to the said rocking member and reeds fitted thereto.

7. In a pitch indicator for musical instruments according to claim 6, a pivoted connection between the arm and the rocking bar, and adjustable means preventing relative movement therebetween when desired.

8. In a pitch indicator for a musical instrument, a plurality of tuned reeds fitted to a rocking member, an arm on the rocking member adapted to engage a vibratory portion of the musical instrument, reflectors on the said reeds, means for projecting a beam of light to the said reflectors and an indicating surface disposed in the path of the reflected beam whereby the amplitudes of the reeds may be observed.

9. In a pitch indicator for musical instruments according to claim 6, means for damping the reeds and removing the arm from engagement with the vibratory portion of the musical instrument when the indicator is not in use.

10. A pitch indicator for musical instruments comprising a bracket, extensions on the bracket, resilient members fitted to the extensions, a rocking bar rigidly secured to the free ends of the resilient members, a plurality of tuned reeds mounted on the rocking bar, and an arm rigidly secured to the rocking bar and adapted to bear at its free end upon a vibratory portion of the instrument.

11. In a pitch indicator for musical instruments according to claim 10, partitions secured to the rocking bar and disposed parallel to the tuned reeds, and a transverse member connecting the free ends of the partitions and forming cells or open compartments for the said reeds.

12. In a pitch indicator for musical instruments according to claim 10, an indicating surface, a reflector on the underside of each of the tuned reeds, means for projecting a beam of light on to the reflectors, and corresponding mirrors arranged below the tuned reeds and adapted to reflect the rays of light upwardly on to the indicating surface.

13. In a pitch indicator for musical instruments according to claim 10, arms supported by the bracket, damping members carried by the said arms and means for causing the damping members to engage the upper and lower sides of the said reeds adjacent to the free ends thereof.

14. A pitch indicator for musical instruments com-prising a bracket, extensions on the bracket, resilient members fitted to the extensions, a rocking bar rigidly secured to the free ends of the resilient members, a plurality of tuned reeds mounted on the rocking bar, an arm rigidly secured to the rocking bar and adapted to hear at its free end upon a vibratory portion of the instrument, a pair of spindles supported by the bracket, clownwardly and forwardly extending arms on the upper spindle, a damper fitted to the said arms below the reeds, forwardly and upwardly extending arms on the lower spindles, a damper on the last-mentioned arms disposed above the tuned reeds, resilient members connecting the free ends of the opposed arms, and springs for normally maintaining the dampers in engagement with the tuned reeds.

15. In a pitch indicator for musical instruments according to claim 14, depending lugs on the forwardly and downwardly projecting arms, co-acting stops on the arms fitted to the lower spindles, a downwardly extending arm on the lower spindle and means for displacing the last mentioned arm against the action of the springs, whereby the dampers may be removed from engagement with the said reeds.

16. A pitch indicator for musical instruments according to claim 14, wherein the springs for normally retaining the dampers in engagement with the tuned reeds are so arranged as to displace the arm and move the same from engagement with the vibratory portion of the instrument when the indicator is not in use.

17 A pitch indicator for musical instruments comprising a bracket, extensions on the bracket, resilient members fitted to the extensions, a rocking bar rigidly secured to the free ends of the resilient members, a plurality of tuned reeds mounted on the rocking bar, an arm rigidly secured to the rocking bar and adapted to bear at its free end upon a vibratory portion of the instrument, an indicating surface, a reflector on the underside of each of the tuned reeds, means for projecting a beam of light on to the reflectors, corresponding mirrors arranged below the tuned reeds and adapted to reflect the rays of light upwardly on to the indicating surface, and means for adjusting the mirrors in two planes disposed at right angles to each other whereby the position of the reflected rays may be accurately controlled.

18. In a pitch indicator for musical instruments acording to claim 17, brackets fitted to the body of the instrument, holders carrying the mirrors supporting screws passing through the brackets and holders, and springs interposed between the brackets and holders whereby the said mirrors may be tilted both longitudinally and laterally.

19. A pitch indicator for musical instruments comprising a bracket, a resilient members fitted to the bracket, a rocking bar sup ported by the resilient members, a plurality of tuned reeds secured to the rocking bar, an arm pivoted to the rocking bar and adapted to bear at its free end on a vibratory portion of the musical instrument, a cam supported 'by the rocking bar and adapted to bear against the said arm, a spring for maintaining the arm in engagement with the cam and THEON NUMA MIRFIELD. 

